Effects of regular ingestion of black tea on haemostasis and cell adhesion molecules in humans

Abstract

Objective: To assess the effects in humans of regular ingestion of black tea on haemostasis-related variables and cell adhesion molecules. Design: Twenty-two subjects were recruited from the general population to a randomised-controlled crossover study. Subjects stopped drinking tea, apart from that provided, for the duration of the study. During a 4-week baseline period all subjects drank 5 cups=day (250 ml) of hot water. The effects of 5 cups=day of black tea for 4 weeks were then compared with hot water. Platelet aggregation in response to three doses of collagen and ADP, plasma concentrations of coagulation and fibrinolytic factors (fibrinogen, factor VII, tPA, PAI-1) and plasma concentrations of cell adhesion molecules (soluble P-selectin, E-selectin, ICAM-1, VCAM-1) were assessed twice, one week apart, at the end of each period. Twenty-four hour urinary concentration of 4-O-methylgallic acid (4OMGA), assessed once at the end of each period, was used as a marker of black tea polyphenol intake. Results: The 24 h urinary excretion of 4OMGA was increased during regular ingestion of black tea in comparison to hot water (P<0.0001). Black tea resulted in lower soluble P-selectin (P ¼ 0.01) in comparison to hot water, but did not influence other adhesion molecules. Soluble P-selectin was significantly correlated with mean collagenstimulated platelet aggregation at baseline (r ¼ 0.61, P ¼ 0.003), and during regular ingestion of hot water (r ¼ 0.70, P<0.0001) and black tea (r ¼ 0.51, P ¼ 0.01). However, platelet aggregation was not different between the black tea and hot water periods for collagen-or ADP-stimulated aggregation at any dose. Coagulation and fibrinolytic factors were also not different between periods. Conclusions: The effect of black tea on soluble P-selectin provides a potential mechanism for cardiovascular benefits of regular ingestion of tea.

The effects of tea on psychophysiological stress responsivity and post-stress recovery: a randomised double-blind trial

“…Michelson et al (2001) have argued that the measurement of platelet-leukocyte aggregates by flow cytometry provides a more accurate assessment of platelet activation than other measures. The polyphenols in black tea have previously been shown to inhibit platelet activation in vitro (Formica and Regelson 1995;Neiva et al 1999), but two studies comparing tea and water administration over 4 weeks did not show any effect on platelet aggregation stimulated by collagen, ADP or thrombin receptor activating peptide (Duffy et al 2001;Hodgson et al 2001). Our results may have been due to the longer period of administration (6 weeks) or the method of assessing platelet activation.…”

Regular Daily Intake of Black Tea Improves Oxidative Stress Biomarkers and Decreases Serum C-Reactive Protein Levels in Type 2 Diabetic Patients

“…We found no significant response of blood fibrinogen levels to daily consumption of up to 4 cups of BTE. This finding is in accord with other human studies [69][70][71] .…”

Evidence for a protective effect of polyphenols-containing foods on cardiovascular health: an update for clinicians

“…Consumption of one litre per day of black tea rich in gallic acid, flavanols, tannins, theaflavins and thearubigins was shown to inhibit platelet activation by 4-10% [Steptoe et al 2007]. Two older studies on tea consumption did not find significant effects on platelet function [Duffy et al 2001b;Hodgson et al 2001]. In 2008, Natella and colleagues demonstrated that the acute intake of 200 ml of coffee mainly providing chlorogenic acid as phenolic compound also had significant anti-aggregatory effects [Natella et al 2008].…”